The present invention relates to a method and an apparatus for magnetizing a permanently magnetizable element associated with a magnetic field sensor structure, for monitoring the alignment of a magnetic field, to an arrangement of a magnetic field sensor element with a permanently associated, non-magnetized hard magnetic material structure, as well as to a method of inscribing a magnetization into a magnetoresistive sensor structure and for protecting a sensor structure against external magnetic fields.
Magnetic field sensors are used, for example, for incremental velocity measurement or as angle sensors. Therefore, frequently magnetoresistive (MR) or giant magnetoresistive (GMR) sensor chips are used, which can detect a change of an external magnetic field. This external magnetic field can be generated, for example, in angle sensors, by a so-called magnetic field, which is mounted above the sensor chip on a shaft/axis. Rotating metal wheels or perforated discs are frequently used for generating a required magnetic field deflection when using magnetic field sensors for velocity measurement. In this case, a back-bias magnet, which is generally behind the magnetic field sensor, generates the magnetic field to be deflected.
In any case, the exact positioning of the magnet generating the external magnetic field, such as the back-bias magnet or the magnetic pill, and the exact direction of magnetization in relation to the magnetic field sensor structure, such as the MR/GMR sensor chip in the above-mentioned example, are of significant importance for an exact mode of operation.